The true identity of Dixa modesta Johannsen (Diptera: Dixidae) resolved: synonymy of Dixa similis Johannsen, designation of the Dixa ubiquita species group, and description of three new eastern Nearctic species
Author
Moulton, John K.
text
Zootaxa
2017
4216
3
247
260
journal article
37359
10.5281/zenodo.231794
61dd696e-205c-47b2-b5b0-200b46743fc0
1175-5326
231794
4015302B-3141-4281-94E2-4D9966681F70
Dixa elkmontensis
sp. nov.
(
Figs 15–17
,
22
)
Type
material.
HOLOTYPE
,
♂
labeled: “
USA
: TN:
SEVIER COUNTY
/
Middle Frk. Little River
/ds of
Elkmont CG
/
N35°39′59.52″
W83°35′27.89″
,
626 m
/
26.vii.2005
/
J.K. Moulton
”; “
HOLOTYPE
/
Dixa
/
elkmontensis
/
J.K. Moulton
[red label]” (
CNC
)
.
PARATYPES:
Same data as holotype, 4♂ and 5♀ to CNC and 5♂ and 5♀ to USNM.
Additional material examined
.
USA
:
TN:
SEVIER COUNTY
,
Middle Frk. Little River
, d/s of
Elkmont CG
,
N35°39′59.52″
W83°35′27.89″
,
626 m
,
26.vii.2005
, JKM (
15♂
,
2♀
)
; Same data,
16.vii.2011
(7♂, 4♀, 1L); Same data,
15.vi.2012
(57♂, 13♀, 5L).
Diagnosis.
This species can be distinguished from
D. ubiquita
sp. nov.
and
D
.
vockerothi
sp. nov.
by the following characters:
Morphological
. Basal gonocoxal lobe with apex subovoid, directed posterodorsally; proximal lobe of SES acute, with thin, strap-like connection to proctiger; apical lobe of SES broad, with apex directed ventrally.
Molecular.
Within the 66 nucleotides (22 codons) shown (
Fig. 35
) a thymine at position 26 (vs. adenine) and a thymine at position 38 (vs. cytosine) serve to distinguish this species from the other two. Within the encompassing amplified fragment of BZF,
D. elkmontensis
sp. nov.
is 4.5% divergent from
D. ubiquita
sp. nov.
and 9.1% divergent from
D. vockerothi
sp. nov.
(JK Moulton, unpublished).
FIGURES 12–20.
Male terminalia (rotated orientation),
12,
Dixa ubiquita
sp. nov.
, lateral view;
13,
D. ubiquita
sp. nov.
, ventral view;
14,
D. ubiquita
sp. nov.
, terminal view;
15,
D. elkmontensis
sp. nov.
, lateral view;
16,
D. elkmontensis
sp. nov.
, ventral view;
17,
D. elkmontensis
sp. nov.
, terminal view;
18,
D. vockerothi
, lateral view;
19,
D. vockerothi
, ventral view;
20,
D. vockerothi
, terminal view. Scale bar = 50 µm.
Description. Male.
Same as
D. ubiquita
sp. nov.
, except as follows: Wing length (
n
=10) 3.4–4.1 (avg=3.7) mm.
Terminalia
(
Figs 15–17
): Apex of basal gonocoxal lobe narrower (ca. 1/3–2/
5X
depth of gonocoxite at midpoint in lateral view;
Fig. 15
) and less squared.
Female.
Wing length (
n
=10) 3.4–3.9 (avg=3.7) mm. Not reliably separated from
D. ubiquita
sp. nov.
or
D. vockerothi
sp. nov
.
Etymology.
Named for the Elkmont area of Great Smoky Mountains National Park (GSMNP), location of the
type
and only known locality.
Distribution.
Known only from the upper reaches of Little River (East Prong) in the Elkmont region of GSMNP (
Fig. 34
).
Remarks.
This species inhabits the widest lotic watercourse (10+m;
Fig. 31
) of any known eastern Nearctic
Dixa
species and is the only dixid found in this section of Little River. During warm summer evenings, individuals of this species, particularly males, are readily attracted to UV lights, likely the result of swarming behavior. Morphologically and molecularly, this species is more closely related to
D. ubiquita
sp. nov.
than to
D
.
vockerothi
sp. nov.
The shape of the basal gonocoxal lobe is intermediate to the character states observed in
D. ubiquita
sp. nov.
and
D. vockerothi
sp. nov.